This invention is concerned with a method for elevator DC drive motor speed control stabilization, including a speed regulator in which speed and current data are used as feed-back information.
DC motors are popular as elevator drive motors because their speed is adjustable and they are vibration-free. However, due to complicated theory, it is extremely difficult to achieve a reliable speed control system for high-quality DC motors, resulting in speed deviations from the instructions provided by the speed regulator. Such deviations include too low an acceleration rate, temporary over-speed as well as speed fluctuations following the acceleration phase and when the elevator is being stopped at a floor.
In ordinary blocks of flats, conventional technology ensures adequate performance because the elevators are relatively slow. Speed control errors are, however, accentuated in high-speed elevators, which is the reason for the fairly poor performance of known elevators. If the elevator is fast, its passage is inconvenient and jerky; in order to achieve smooth travel, speed must be reduced.
This invention is designed to avoid the problems associated with the speed control of high-speed elevators. Characteristics of the method for elevator DC drive motor speed control stabilization is that the current regulator is approximated by means of an ideal integrator. The mathematical model thereby obtained is used for determining the time constants and amplification of the control system speed loop or loops, and these system parameters are compensated with corresponding short design speed accentuations to produce a practically delay-free control system. As a result, control signal generation is simplified because real speed follows closely the control voltage. In addition, accurate stopping is achieved, which, apart from being more convenient for the passangers, permits the use of a a narrower "stopping window" ensuring higher stopping accuracy.
By a stopping window we mean an area extending to the both sides of a floor level where the elevator can stop without requiring any rectification. Consequntly, the elevator cannot stop outside this window; if it tries to, it moves in creep motion until it finds the correct window.